fix(cli): read stdin lazily so open pipes don't hang the CLI

[l2ysho]

Note

TL;DR — The CLI read stdin at startup for every command, so a pipe that stays open hung it forever. Now it only reads stdin when a command wants it, and a read nobody asked for gives up when the pipe goes quiet.

Closes #1206.

The startup read

_shared.ts read stdin at module scope (export const cachedStdinInput = await readStdin()), so every command blocked on stdin whether or not it uses it. #1294 fixed the socket case (a spawned child's stdio: 'pipe'), but a named pipe has no wait deadline — the read never ended and the command never even ran, so 1.8.0 still hangs with no output at all:

sleep 60 | apify --version   # 1.8.0: hangs, no output

Read stdin only where it's asked for: a - arg/flag, apify run without --input, push-data/push-items without an item arg. readStdin() memoizes, since stdin can only be drained once.

Confirmations keyed off hasData, which the eager read flipped to false after draining. Without that read it stays true, so apify <confirm-cmd> < /dev/null would try to prompt on a non-TTY — gated on isTTY instead.

The implicit read

That left one path still hanging. apify run without --input falls back to stdin, and waited there for an end a named pipe never reaches. actors call and actors start share it. Two ways to hang:

apify run < /some/fifo                          # nothing ever sent
(printf '{"a":1}'; sleep 30) | apify run        # sent, then held open

A read the user never asked for now stops at the first quiet gap: each chunk restarts a 2s clock, and when stdin goes silent the CLI uses what arrived. An explicit - is unchanged — it waits for the writer to close, the way cat does.

Trade-off: a writer slower than ~2.5s to its first byte is now ignored (curl slow-endpoint | apify run). Truncation mid-stream stays loud, since the JSON fails to parse. 2s is a judgement call, not a derived number.

Verification

Measured against a build of master and a build of this branch.

stdin	command	before	after
open pipe, no data	--version	hang, no output	405 ms
open pipe, with data	--version	hang, no output	654 ms
closed pipe	--version	exits	exits
spawn stdio: 'pipe' (#1294's case)	--version	exits	exits
open pipe, silent	run in a project	hang	2621 ms, no input
open pipe, sends then holds	run in a project	hang	2619 ms, input used
writer delays 0 / 1 / 2 s, then closes	run in a project	input used	input used
writer delays 4 s, then closes	run in a project	input used	input dropped, 2603 ms

Three new e2e cases, all skipped on Windows (no mkfifo). Each fails on the pre-fix build at the 15s deadline and passes after:

• FIFO on stdin, empty dir — the startup read
• FIFO on stdin, real project, silent — the implicit read
• FIFO on stdin, real project, sends then holds open — asserts the Actor received the input

pnpm run test:local green (540 passed). pnpm run test:e2e:local green (44 passed). No dependency or install-size change.

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